Adventures in Baja:
The UCMexus Field Conference

by Collen Whitney and David Smith  (page 1 of 3)

UCMP Curator and Professor of Integrative Biology Jere Lipps and Professor
of Geology Jorge Ledesma Vázquez of the Universidad Autónoma de Baja
California (UABC) in Ensenada, Mexico, organized an 8-day field conference
that took place Saturday, March 24 through Sunday, April 1 (coinciding
with Cals spring break). Participants included both UC Berkeley and
UABC students (plus a few UCMP staff like us). We delved into the geology,
paleontology and marine biology of the upper two thirds of the Baja
California peninsula, and had the opportunity to exchange ideas with
our neighbors from across the border.Eighteen Berkeley participants (as well as piles of camping gear and
food) headed for Baja, pausing in Ensenada to pick up our five UABC
associates. Professor Ledesma Vázquez, an authority on the geology of
the Baja peninsula, interpreted the geologic features we observed at
many stops along Mexico 1 as we drove south toward Loreto, and Professor
Lipps contributed his expertise in paleontology and marine biology.
Highlights included:

The Santo Tomás valleyThis region was a textbook example of
horst and graben (a graben is a section of the Earths crust that has
subsided between two faults; the horsts are the raised sections of crust
bounding the graben).

Near ErendiraWe explored Cretaceous-aged limestone bearing
the fossils of rudists (large clams) and corals. These were in huge
mounds of reef debris that had not been moved far from their place of
origin. Overlaying these were the remains of a Pleistocene marine terrace,
including the borings of Pleistocene clams (some of the holes still
contained the fossilized clams!). Nearby, Professor Ledesma Vázquez showed us the remains of a mid-Cretaceous island surrounded by later
Cretaceous marine sediments and fossils. The exposures were along the
sea cliffs, so that we also had an opportunity to see the modern Pacific
marine invertebrate and algal biota.

Professor Jere Lipps (center) directs a student to
examine the nearly anoxic muds among the roots of these mangroves at Bahía
de Concepción. Professor Ledesma Vázquez is at left. (photo by David
K. Smith)The Cataviña areaHere we camped on what was once a magma chamber,
that cooled and then was brought to the surface through uplift and erosionthe
very light-colored granite was eroding into rounded boulders and breaking
down into sand. The hilly, boulder-strewn landscape was covered with
the unusual vegetation of the Vizcaino desert subregion, including the
cirio tree (or boojum), and cardon cactus.

Near San IgnacioAs we moved southeast across the peninsula,
evidence of volcanism increased as we passed basalt flows, cinder cones
and volcanic plugs. Amidst the basalt flows we stopped at the desert
oasis of San Ignacio. Here, groundwater surfaces to form a sizeable
river, irrigating groves of imported European date palms.